Regensburg 2019 – wissenschaftliches Programm
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MM: Fachverband Metall- und Materialphysik
MM 27: Methods in Computational Materials Modelling (methodological aspects, numerics)
MM 27.11: Vortrag
Mittwoch, 3. April 2019, 17:45–18:00, H44
Ab initio study of tetragonal and trigonal bcc-fcc trans- formations in Ti-Al-Mo system — Neda Abdoshahi1, •David Holec1, Martin Friák2, and Mojmir Šob2 — 1Department of Ma- terials Science, Montanuniversität Leoben, Franz-Josef-Strasse 18, A- 8700 Leoben, Austria — 2Institute of Physics of Materials, Academy of Sciences of the Czech Republic, Žižkova 22, CZ-616 62 Brno, Czech Republic
Motivated by a recently reported martensitic transformation in the Ti-Al-Mo intermetallic system, we employed first principles calculations to study this process on an atomic level. Our calculations reveal a spontaneous transformation from the unstable β o (bcc ordered) to the stable γ phase: there is no energy barrier along the transformation path, and an overall energy difference is *140 meV/at. for β o * γ. It is further shown that a chemical disorder reduces the driving force (total energy difference) for the β * γ dis transformation to essentially "zero" and introduces a small energy barrier of about 10 meV/at..
Next we have investigated a trigonal transformation path, connecting bcc, simple cubic (sc) and fcc structures. Not only it yields a high energy barrier of * 890 meV/at. for β 0 * γ * transformation, but it also leads to another fcc-based ordered binary compound, namely the L1 2 structure (γ * ) instead of the true TiAl L1 0 (γ) ground state. Consequently we exclude the trigonal transformation path for the MTs in TiAl. In the final part we explore the impact of Mo on the stabilization of the β/β o TiAl with respect to the γ phase.